Polynemids of India

8/3/2019 Polynemids of India

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POLYNEMIDS OF INDIA

by

Renjith.R.K

FRM 225



Polynemids or Threadfins

•

Order: Perciformes• Important food fish . Some may attain 2 meters length

• Can be identified as a family by –

similarity in appearance

conical snoutinferior mouth

condition of eye (adipose eyelid)

well separated dorsal fins

3-16 lower pectoral fin rays (most distinct)• Commercial and sport fishes of tropical , temperate

• Middle , East , Southeast Asia , Australia , South Africa



Classification

of the

family

Polynemidae



Polynemids reported in India

1. Eleutheronema tetradactylum (Shaw, 1804) 2. Filimanus similis Feltes, 1991

3. Filimanus xanthonema (Valenciennes, 1831)

4. Leptomelanosoma indicum (Shaw, 1804)

5. Polydactylus microstomus (Bleeker, 1851)

6. Polydactylus mullani (Hora, 1926)

7. Polydactylus plebeius (Broussonet, 1782)

8. Polydactylus sexfilis (Valenciennes, 1831)

9. Polydactylus sextarius (Bloch and Schneider, 1801)

10. Polynemus paradiseus Linnaeus, 1758



Eleutheronema tetradactylum Fourfinger threadfin



Characters

• Anterior part of lower jaw with small teeth extending ontolateral surface

• Pored lateral-line scales 71 to 80

• Gill rakers 3 to 8 on upper limb, 3 to 10 on lower limb , 6 to 18

total

• gill rakers on anterior parts of upper and lower limbs replaced

by tooth plates with villiform teeth

• 9-12 scale rows above , 13-15 below lateral line

• Pectoral fin membranes vivid yellow when fresh

• 4 small free pectoral filaments



Filimanus similisIndian sevenfinger threadfin



Characters•

Small species• Pored lateral-line scales 45 to 49

• pectoral filaments 7

• 1st filament shortest, not reaching to level of posterior tip of

pelvic fin

3rd and 4th filaments usually longest, its length 25 to 48% of

standard length, reaching to level of anal-fin origin

• Gill rakers 40-49

• scale rows above lateral line 5 to 7 , below 9 to 11



Filimanus xanthonema

Yellowthread threadfin



Characters • Posterior margin of maxilla extending slightly beyond level of

posterior margin of adipose eyelid• Pored lateral-line scales 43 to 52 ;

• scale rows above lateral line 5 to 8, below 9 to 12 .

• Gillrakers (total) 36 to 46

• base of pectoral filaments white, becoming yellowish whiteon posterior tips; base

of pelvic fin white, other parts yellowish.

• pectoral filaments usually 6 on each side but occasionally 5

on each side, or asymmetrically 5 and 6 or 6 and 7, firstfilament shortest, not reaching to level of posterior tip of

pelvic fin; third and fourth filaments usually longest



Leptomelanosoma indicum

Indian threadfin



Characters

• Elongate body and head

• 5 pectoral filaments , 1st one not reaching up to pelvic fin

origin , fifth filament longest

•

Pored lateral-line scales 69-72 (mode 70)• lateral line simple, extending from upper end of gill opening

to upper end of lower caudal-fin lobe

• scale rows above lateral line 7 or 8 , below 9 -12 .

•Gill rakers 8 or 9 on upper limb, 10 -12 on lower limb, 18 -21total.



Polydactylus microstomusSmallmouth threadfin



characters

• Pectoral filaments 5, first filament shortest, not reaching

to or just reaching to level of pelvic-fin origin

• second to fourth pectoral filaments just short of or

extending slightly beyond level of pelvic-fin origin; fifth

pectoral filament longest

• body and fins tinged with yellowish silver colour

• Gillrakers 10-14 on upper limb, 13-18 on lower limb,

24-33 total.

• Swimbladder present, well developed

• a large black spot anteriorly on lateral line.



Polydactylus mullani

Arabian blackspot threadfin



Characters

•Depth of posterior margin of maxilla less than eye diameter

• pectoral filaments 7 (rarely asymmetrically 6 and 7)

1st and 2nd - not reaching to level of pelvic-fin origin

3rd to 6th -extending beyond level of pelvic-fin origin

7th -longest, extending well beyond level of posterior tip of

pectoral fin

• Pored lateral-line scales 46-50

• scale rows above lateral line 5-7 below 9 or 10

• Gill rakers 13-16 on upper limb, 18-21 on lower limb, 31-35

total.

• Endemic and common in the northern Arabian Sea



Polydactylus sexfilisSixfinger threadfin



Characters


•1

st

-shortest, not reaching to level of pelvic-finorigin;

2nd to 5th - extending beyond level of pelvic-fin

origin;

6th -longest, not extending beyond level of posteriortip of pelvic fin


• scale rows above lateral line 8-10 , below 12-14

• Gill rakers 11-14 on upper limb, 15-18 on lower

limb ,total 27-31

• Robust body



Polydactylus sextarius

Blackspot threadfin



Characters


1st filament shortest;6th pectoral filament longest, 20-29% of standard length


• scale rows above lateral line 5 or 6 , below 8-11

• Gill rakers 10-14 on upper limb, 14-18 on lower limb,

total 25-30

• Swim bladder atrophied, like a fine string.

• pectoral-fin membrane white with scatteredmelanophores

• large black spot anteriorly on lateral line.



Polydactylus plebeius

Striped threadfin



Characters

• Pectoral filaments 5

1st

- shortest, just reaching to level of pelvic-fin origin2nd to 4th - not reaching to level of posterior tip of pelvic

fin;

5th - longest, 22 to 40% of standard length, reaching or

extending beyond level of posterior tip of pelvic fin


• scale rows above lateral line 8 or 9 , below 12 or 13

•

Gillrakers 9-14 on upper limb,13-18 on lower limb, total24-32

• 7 or 8 prominent dark stripes along scale rows above

lateral line, 7 to 9 faint stripes below.



Polynemus paradiseus

Paradise threadfin



Characters • pectoral filaments 7;

1st

-shortest, not reaching to level of posterior tip of pelvic fin2nd - not reaching to or extending slightly beyond level of

posterior tip of pelvic fin

3rd -just reaching to or not reaching to level of anal-fin origin

4th

- reaching posterior base of anal fin or to caudal-fin base5th to 7th - longer than total length

6th- longest, its length 181 to 248% of standard length

• Pored lateral-line scales 66 to 71

• scale rows above lateral line 6 or 7 , below 10 to 12

• Gillrakers 12 -14 on upper limb, 17 -20 lower ,total 30 to 34

• Swim bladder absent



Key for identification of polynemids in India

1. Anterior part of lower jaw with small teeth extending on to

lateral surface , adjacent part of tipabsent…………………………….……………………………Eleutheronema

1a.Pored lateral line scales 71-80. scale row 9-12 above, 13-14

below . Pectoral membranes vivid yellow when fresh,exceptin large specimens(over 350 mm ) ……………..E.tetradactylum

2.Anal fin base length less than head length, fin rays 10-18 ,space

separating premaxillary teeth bands 2 or more times widerthan bands, basispenoid not in contact with

prootic………………………………………………………………..Filimanus



2a. Gill rakers 40-49 (mode39)…………………………….………….F.similis

2b.Pectoral filaments 6 (occasionally 7) or asymmetrically 5 or 6 ,or 6 or 7 , gill rakers 36-46 (mode

41)………………………………………..…..…………………..F.xanthonema

3. Tip of upper and lower caudal fin lobes filamentous………………………………………………………….………Leptomelanosoma

3a. Pectoral fin rays 12-14 . 5 filaments. 1st filament short and not

reaching up to pelvic finorigin……………………………………………………………….L.indicum



4. Tips of upper and lower caudal fin lobes not filamentous ,

sphenotics not exposed dorsally . Swim bladder absent or if

present found without

appendages…………………………………………………..… Polydactylus

4a. A large black spot present on anterior lateral line . ………….5

4b. No large black spot anteriorly on lateral line…………………….6

5. Pectoral filaments 5.body and fins tinged with

yellowish silver……………………………………..…...P . Microstomus

6. Pectoral filaments 6 or 7 , body and fins tinged with silver……7



7a.Pectoral filaments 7 . Second spine of 1st dorsal fin more

robust than other dorsal fin

spines……………………………………………………………...….P . Mullani

7b.Pectoral filaments 6 , all spines of 1st dorsal fins are of similar

thickness. Gill rakers 25-30(mode 28). Second dorsal fin

spines short(6% of standard length). Atrophied swim

bladder………………………………………………………..…… P . sextarius

7c. Lateral line unbranched on caudal-fin base, extending to

posterior margin of lower caudal-fin lobe, thickness of all

spines of first dorsal fin similar . Pored lateral line 8-9 aboveand 12-13 below …………………………………………..…..P . Plebeius

7d. Toothed vomer. Pored lateral line 61-67. orbit diameter

9%...................................... ...........................P . sexfilis



8. Posterior margin of preopercle serrated …….………Polynemus

8b. Pored lateral line scales 66-71( mode 70 ) . Scale row above

lateral line 6-7, below 10-12 . (mode 11).

Gill raker 30-34 . Occipital profile straight .

Swim bladder absent…………….....……………………P . Paradiseus



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Polynemids of India